Triple Gold Shells
From the Super Mario Wiki, the Mario encyclopedia
Triple Gold Shells are clusters of three Gold Shells appearing as an unlockable item in Mario Kart Arcade GP DX. Three Gold Shells can be thrown one-by-one by the player from the front. They function like Black Shells, but they instead home in on the driver in front of the player, like a Red Shell. They explode upon impact of a wall, obstacle, or other racer, causing any racers caught in the blast to be knocked over for a brief moment.